It won't be everyone's cup of tea but a slice of toast believed to have been served to Prince Charles for breakfast on the day he married Diana is to be auctioned.

Rosemarie Smith, from Derby, took the leftover slice from a tray after visiting her daughter at Buckingham Palace just hours before the royal wedding at St Paul's Cathedral in July 1981.

It is thought the slice of white toast could fetch up to £500 when it goes under the hammer at Charles Hanson Auctioneers in Etwall, Derby, on July 19.

More than 750 million people tuned in around the world to see Prince Charles marry Lady Diana Spencer on July 29, 1981.

Mrs Smith said: "At the time my daughter was a maid at the Palace and one of her duties was to collect Prince Charles's breakfast tray from outside his room.

"I was with her in the corridor and saw that Prince Charles had left some toast on the tray. I had been thinking about a keepsake from the wedding and saw the toast and thought to myself: 'Why not'?"

Since then she has kept the slice of toast in a cup on a shelf at home.

The 83-year-old added: "We hadn't talked about it much down the years but William and Kate's wedding last year and then the Queen's Jubilee has made the royals more popular than ever. That got me thinking that my toast could be worth a bit of money.

"I just wandered into the auctioneers out of curiosity and asked them if it was worth anything. I was pleasantly surprised to hear them agree with me that it could be of quite some value to royal collectors."